1. Field of Invention
The field of the currently claimed embodiments of this invention relates to surgical instruments and systems that incorporate the surgical instruments, and more particularly to systems and surgical instruments that have integrated optical sensors.
2. Discussion of Related Art
Vitreoretinal surgery addresses prevalent sight-threatening conditions such as retinal detachment, macular pucker, macular holes, and vision threatening conditions in which epiretinal scar tissue is removed. The technical demands placed on the surgeon by these procedures are extreme. In current practice, retinal surgery is performed under an operating microscope with free-hand instrumentation. Human limitations include an inability to clearly visualize surgical targets, physiological hand tremor, and lack of tactile feedback in tool-to-tissue interactions. In addition, tool limitations, such as lack of proximity sensing or smart functions, are important factors that contribute to surgical risk and reduce the likelihood of achieving surgical goals. Current instruments do not provide physiological or even basic interpretive information, e.g. the distance of the instrument from the retinal surface, the depth of instrument penetration into the retina or an indication of the force exerted by the instrument on the retinal tissues. Surgical outcomes (both success and failure) are limited, in part, by technical hurdles that cannot be overcome by current instrumentation. For example, in the most technically demanding cases, there may not be a set of tools that allows the “typical” retina surgeon to remove sufficient epiretinal scar tissue to assure surgical success.
Peeling of epiretinal membranes (ERMs) from the surface of the retina is one example where there is a need for improved surgical instruments and systems. ERM peeling is a common and extremely demanding surgical procedure. ERMs are scar tissue that form on the surface of the retina, contract, and compromise retinal function. ERMs are present in 2-6.4% of people (Sjaarda R. N., Michels R. G., Macular pucker. In: S J Ryan, Editor, Retina. Vol. 3. (2nd ed), Mosby, St. Louis. pp. 2301-2312. (1994)). Visual dysfunction resulting from ERMs includes: blurred vision, image distortion, and altered image size. Surgical removal of an ERM involves identifying or creating an “edge” that is then grasped and peeled. Some ERMs provide clear visual evidence of edges that may be grasped. Others require creation of an edge by the surgeon. This may be performed by incising the membrane surface, by bluntly creating an edge, or by gently grasping the membrane with a forceps and creating a tear in the ERM. Each of these maneuvers requires excellent visualization, high levels of manual dexterity and micro-instrumentation. Furthermore, this procedure is performed with a comparatively large metal instrument without tactile sensation. During this time, a patient's involuntary and voluntary movement must be manually compensated by the surgeon while the instrument is in direct contact with fragile intraocular tissue. Incorrect micron-magnitude movements can cause retinal tears, retinal detachment, visual field defects, retinal hemorrhage, local retinal edema, nerve fiber layer injury, and macular holes, all of which can contribute to blindness.
Optical coherence tomography (OCT) provides very high resolution (micron scale) images of anatomical structures within the retina. Within Ophthalmology, OCT systems typically perform imaging through microscope optics to provide 2D cross-sectional images (“B-mode”) of the retina. These systems are predominantly used for diagnosis, treatment planning, and, in a few cases, for optical biopsy and image guided laser surgery.
ERMs are recognized by Optical Coherence Tomography (OCT) as thin, highly reflective bands anterior to the retina. A potential dissection plane between the ERM and the retina is usually clearly visible in the scan, but is invisible to the surgeon through an operating microscope, even with very high magnification. In other work, our laboratory has explored registration of preoperative OCT images to intraoperative microscope images to aid in identifying ERM edges for initiating ERM removal. However, epiretinal membranes can grow and further distort retinal architecture. It is therefore, unclear whether preoperative images would provide a useful guide if the interval between the preoperative image acquisition and surgery allows for advancement of the ERM.
There thus remains the need for improved instruments and systems for precision manipulation of objects, such as, but not limited to, microsurgical applications.